It’s a problem of psychology and scale. The communist system becomes susceptible to bad actors the larger the group becomes.
In point of fact: I fully agree that many Latin countries, absent US bullshittery, intervention, and fomenting of coups in the first Cold War, would probably mostly have wound up being successful.
But I absolutely do not agree that the USSR or the PRC should be held up as paragons of virtue of what a Communist system should be. They were very quickly corrupted by authoritarian leaders and cliques from the get go, which is genuinely antithetical to true communism.
Lmao this is precisely how I thought this would turn out.